A Fully Biobased Aromatic Polyester Polyol for Polyisocyanurate Rigid Foams: Poly(diethylene furanoate)

Abstract

Aromatic polyester polyols are often used in polyurethane rigid foam (PUR) and polyisocyanurate (PIR) synthesis, since they offer higher rigidity than polyether polyols. Herein, a route toward fully biobased aromatic polyester polyols was investigated using sugar-based 2,5-furandicarboxylic acid (FDCA) and diethylene glycol (DEG), enabling a direct one-step synthesis of a fully biobased aromatic polyester polyol, poly­(diethylene furanoate) (PDEF), for applications in PIR rigid foam. Therefore, reaction conditions were optimized to obtain PDEF as a processable polyol with OH values and remaining unreacted DEG similar to a commercial, petroleum-based polyol. The processability was improved by either copolymerizing 10–20 mol % of a biobased aliphatic dicarboxylic acid, like succinic acid (SA) or adipic acid (AA), maintaining the fully biobased character of the polyol, or copolymerization with phthalic acid. The fully biobased polyester polyols were successfully prepared on a 100 g scale of dicarboxylic acids. Subsequent application in PIR rigid foam showed similar density, thermal conductivity, flame behavior, and compressive strength if compared to the rigid foam obtained from a commercial polyol. Thus, fully biobased PDEF can substitute petroleum-based aromatic polyester polyols in PIR applications.

Renewable and Biodegradable Polyurethane Foams with Aliphatic Diisocyanates

“…The resulting aromatic polyester polyol was characterized using nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR) to confirm its chemical structure, as well as gel permeation chromatography (GPC) to determine the polyol's polydispersity index (PDI) and molecular weight (MW) (Supporting Information, Figures S1−S5). Formation of an ester bond between FDCA and PDO was confirmed by the presence of an ester-attached methylene group from the PDO backbone with a distinguished ester carbonyl group at δ = 172.58 ppm in the 13 C NMR spectra and FTIR peaks at 1730 and 1170 cm −1 , indicating the formation of the ester carbonyl group. GPC analysis demonstrated that the polyol has a PDI of 1.75 and an M n of 3467 g/mol.…”

“…To lower viscosities even further, they added 10−20 mol % succinic acid or adipic acid to maintain the fully biobased character of the polyol, which further increased the processability of the FDCA-based polyol. 13 PPFA was subjected to viscosity analysis carried out at 65 °C, resulting in a viscosity of 2380 cP compared to that of the commercial polyol having a viscosity of 2500−2900 cP at 50 °C. While the cP is lower for PPFA at a higher temperature compared to that of the cupsole polyol, PU foam manufacturing can utilize temperatures upward of 80 °C during processing, resulting in an industrially relevant polyester polyol.…”

“…Another study by Rhein et al utilized polyethylene glycol at various equivalences to obtain processable high molecular weight FDCA-based polyols. To lower viscosities even further, they added 10–20 mol % succinic acid or adipic acid to maintain the fully biobased character of the polyol, which further increased the processability of the FDCA-based polyol . PPFA was subjected to viscosity analysis carried out at 65 °C, resulting in a viscosity of 2380 cP compared to that of the commercial polyol having a viscosity of 2500–2900 cP at 50 °C.…”

“…Nuclear Magnetic Resonance Spectroscopy (NMR). The 1 H and 13 C NMR spectra were recorded on a JEOL ECA 400 instrument at ambient temperature. The chemical shifts for the 1 H NMR spectra were reported in parts per million relative to the central singlet solvent signal of DMSO at 2.5 ppm.…”

“…Other research explores copolymerization of FDCA to increase industrial relevance and broaden applications. 12 Recently, the preparation of flameretardant rigid polyurethane foams using FDCA as an aromatic polyol was reported, 13 but little is known about FDCA's potential in PU foam systems. Here, we utilize FDCA as an aromatic monomer to provide aromatic moieties on the polyol side of PU foam formulations with aliphatic diisocyanates.…”